MSHTA Execution with Suspicious File Extensions

Status: test
Severity: high
Log source: product windows, category process_creation
Author: Diego Perez (@darkquassar), Markus Neis, Swisscom (Improve Rule), Swachchhanda Shrawan Poudel (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects execution of mshta.exe with file types that looks like they do not typically represent HTA (HTML Application) content, such as .png, .jpg, .zip, .pdf, and others, which are often polyglots. MSHTA is a legitimate Windows utility for executing HTML Applications containing VBScript or JScript. Threat actors often abuse this lolbin utility to download and execute malicious scripts disguised as benign files or hosted under misleading extensions to evade detection.

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1059.007` Command and Scripting Interpreter: JavaScript
Stealth	`T1140` Deobfuscate/Decode Files or Information, `T1218.005` System Binary Proxy Execution: Mshta

Event coverage

Provider	Event	Title
Sysmon	Event ID 1	Process creation

Rule body yaml

title: MSHTA Execution with Suspicious File Extensions
id: cc7abbd0-762b-41e3-8a26-57ad50d2eea3
status: test
description: |
    Detects execution of mshta.exe with file types that looks like they do not typically represent HTA (HTML Application) content,
    such as .png, .jpg, .zip, .pdf, and others, which are often polyglots. MSHTA is a legitimate Windows utility for executing HTML Applications
    containing VBScript or JScript. Threat actors often abuse this lolbin utility to download and
    execute malicious scripts disguised as benign files or hosted under misleading extensions to evade detection.
references:
    - http://blog.sevagas.com/?Hacking-around-HTA-files
    - https://0x00sec.org/t/clientside-exploitation-in-2018-how-pentesting-has-changed/7356
    - https://learn.microsoft.com/en-us/previous-versions/dotnet/framework/data/xml/xslt/xslt-stylesheet-scripting-using-msxsl-script
    - https://medium.com/tsscyber/pentesting-and-hta-bypassing-powershell-constrained-language-mode-53a42856c997
    - https://twitter.com/mattifestation/status/1326228491302563846
    - https://www.virustotal.com/gui/file/c1f27d9795a2eba630db8a043580a0761798f06370fb1317067805f8a845b00c
author: Diego Perez (@darkquassar), Markus Neis, Swisscom (Improve Rule), Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2019-02-22
modified: 2025-05-12
tags:
    - attack.stealth
    - attack.t1140
    - attack.t1218.005
    - attack.execution
    - attack.t1059.007
    - cve.2020-1599
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith: '\mshta.exe'
        - OriginalFileName: 'mshta.exe'
    selection_cli:
        CommandLine|contains:
            - '.7z'
            - '.avi'
            - '.bat'
            - '.bmp'
            - '.conf'
            - '.csv'
            - '.dll'
            - '.doc'
            - '.gif'
            - '.gz'
            - '.ini'
            - '.jpe'
            - '.jpg'
            - '.json'
            - '.lnk'
            - '.log'
            - '.mkv'
            - '.mp3'
            - '.mp4'
            - '.pdf'
            - '.png'
            - '.ppt'
            - '.rar'
            - '.rtf'
            - '.svg'
            - '.tar'
            - '.tmp'
            - '.txt'
            - '.xls'
            - '.xml'
            - '.yaml'
            - '.yml'
            - '.zip'
            - 'vbscript'
            # - '.chm'  # could be prone to false positives
            # - '.exe'
    condition: all of selection_*
falsepositives:
    - False positives depend on scripts and administrative tools used in the monitored environment
level: high

Stages and Predicates

Stage 0: `condition`

all of selection_*

Stage 1: `selection_img`

selection_img:
    - Image|endswith: '\mshta.exe'
    - OriginalFileName: 'mshta.exe'

Stage 2: `selection_cli`

selection_cli:
    CommandLine|contains:
        - '.7z'
        - '.avi'
        - '.bat'
        - '.bmp'
        - '.conf'
        - '.csv'
        - '.dll'
        - '.doc'
        - '.gif'
        - '.gz'
        - '.ini'
        - '.jpe'
        - '.jpg'
        - '.json'
        - '.lnk'
        - '.log'
        - '.mkv'
        - '.mp3'
        - '.mp4'
        - '.pdf'
        - '.png'
        - '.ppt'
        - '.rar'
        - '.rtf'
        - '.svg'
        - '.tar'
        - '.tmp'
        - '.txt'
        - '.xls'
        - '.xml'
        - '.yaml'
        - '.yml'
        - '.zip'
        - 'vbscript'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`CommandLine`	match	`.7z` corpus 2 (sigma 2) `.avi` `.bat` corpus 11 (sigma 9, elastic 1, kusto 1) `.bmp` corpus 2 (sigma 2) `.conf` `.csv` corpus 2 (sigma 2) `.dll` corpus 16 (sigma 16) `.doc` corpus 4 (sigma 4) `.gif` corpus 8 (sigma 8) `.gz` `.ini` `.jpe` `.jpg` corpus 7 (sigma 7) `.json` `.lnk` corpus 3 (sigma 3) `.log` corpus 4 (sigma 4) `.mkv` `.mp3` corpus 2 (sigma 2) `.mp4` `.pdf` corpus 3 (sigma 3) `.png` corpus 7 (sigma 7) `.ppt` corpus 4 (sigma 4) `.rar` corpus 2 (sigma 2) `.rtf` corpus 2 (sigma 2) `.svg` corpus 2 (sigma 2) `.tar` `.tmp` corpus 3 (sigma 3) `.txt` corpus 9 (sigma 9) `.xls` corpus 4 (sigma 4) `.xml` corpus 6 (sigma 4, splunk 2) `.yaml` `.yml` corpus 2 (sigma 2) `.zip` corpus 6 (sigma 5, chronicle 1) `vbscript` corpus 3 (sigma 2, splunk 1)
`Image`	ends_with	`\mshta.exe` corpus 67 (sigma 67)
`OriginalFileName`	eq	`mshta.exe` corpus 22 (sigma 13, splunk 6, elastic 3)

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)

MSHTA Execution with Suspicious File Extensions

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_img`

Stage 2: `selection_cli`

Indicators

Keyboard shortcuts

Search operators

MSHTA Execution with Suspicious File Extensions

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_img

Stage 2: selection_cli

Indicators

Stage 0: `condition`

Stage 1: `selection_img`

Stage 2: `selection_cli`